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https://issues.apache.org/jira/browse/RYA-417?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16320715#comment-16320715
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ASF GitHub Bot commented on RYA-417:
------------------------------------
Github user ejwhite922 commented on a diff in the pull request:
https://github.com/apache/incubator-rya/pull/255#discussion_r160750321
--- Diff:
extras/rya.forwardchain/src/main/java/org/apache/rya/forwardchain/strategy/RoundRobinStrategy.java
---
@@ -0,0 +1,211 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.rya.forwardchain.strategy;
+
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.TreeSet;
+
+import org.apache.log4j.Logger;
+import org.apache.rya.api.domain.RyaType;
+import org.apache.rya.api.domain.StatementMetadata;
+import org.apache.rya.forwardchain.ForwardChainConstants;
+import org.apache.rya.forwardchain.ForwardChainException;
+import org.apache.rya.forwardchain.rule.Rule;
+import org.apache.rya.forwardchain.rule.Ruleset;
+import org.openrdf.model.vocabulary.XMLSchema;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * A simple {@link AbstractForwardChainStrategy} that iterates over every
+ * relevant rule once, and repeats until no rules are relevant.
+ * <p>
+ * Initially, all rules are considered relevant. Iteration 1 executes each
rule
+ * once.
+ * <p>
+ * When a rule produces inferences, all rules that are marked as that
rule's
+ * successors according to the {@link Ruleset} are triggered as potentially
+ * relevant for future execution. If a triggered rule is scheduled to be
+ * executed during the current iteration, nothing changes. If a triggered
rule
+ * has already been executed once during the current iteration, or was not
+ * activated for the current iteration at all, it is flagged to be executed
+ * during the next iteration.
+ * <p>
+ * When an iteration concludes, a new iteration begins with the relevant
set of
+ * rules having been determined during the previous iteration. If there
are no
+ * such rules, forward chaining ends.
+ * <p>
+ * Within each iteration, rules are processed such that a rule which may
trigger
+ * many other rules is given priority over a rule that may be triggered by
many
+ * other rules.
+ * <p>
+ * The observation that one rule may trigger another is based on the
+ * relationships between triple patterns produced and consumed by the
rules in
+ * general, not based on any triples that were actually generated.
Therefore,
+ * there may be false positives but not false negatives: Rules triggered
by the
+ * current rule may or may not produce more triples in response, but any
rule
+ * that could produce triples in response will be triggered.
+ * <p>
+ * The procedure for executing the individual rules is governed by the
+ * {@link RuleExecutionStrategy}. This class uses the strategy's reported
counts
+ * to determine whether or not a rule has produced inferences.
+ */
+public class RoundRobinStrategy extends AbstractForwardChainStrategy {
+ private static final Logger logger =
Logger.getLogger(RoundRobinStrategy.class);
+
+ private final AbstractRuleExecutionStrategy ruleStrategy;
+ private int iteration;
+ private Ruleset ruleset;
+ private Set<Rule> activeNow;
+ private Set<Rule> activeNextIteration;
+ private long inferencesThisIteration;
+ private boolean initialized = false;
--- End diff --
Use an AtomicBoolean for a little bit more thread safety
> Implement a forward-chaining rules engine (SPIN)
> ------------------------------------------------
>
> Key: RYA-417
> URL: https://issues.apache.org/jira/browse/RYA-417
> Project: Rya
> Issue Type: New Feature
> Reporter: Jesse Hatfield
> Assignee: Jesse Hatfield
>
> Implement a forward-chaining reasoner that:
> * Runs as a batch process
> * Operates on user-defined [SPIN|http://spinrdf.org] rules
> * Inserts derived information back into Rya
> * Iterates until no new information can be derived
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